The invention relates to selection of the implementation of a service, and particularly to selection of the implementation of a supplementary service in a mobile communication system.
Mobile communication systems were developed, because there was a need to allow people to move away from fixed telephone terminals without affecting their reachability. The services offered through the terminal equipment of mobile communication systems have developed along with the systems. At the moment, various new forms of service are being planned for the current and particularly for the future third-generation mobile communication systems, such as Universal Mobile Telecommunication System (UMTS) and International Mobile Telecommunication 2000 (IMT-2000). UMTS is being standardized by ETSI (European Telecommunications Standards Institute), whereas ITU (International Tele-communications Union) is standardizing the IMT-2000 system. These future systems are very similar in basic features. The following will describe in greater detail the UMTS system whose architecture is illustrated in FIG. 1. The basic structure of UMTS comprises an access network (AN) and one or more Core Networks (CN). The mobile terminals (MT) of the users are reached by means of the access network. The core network can be any conventional telecommunications network or a future telecommunications network. The mobile terminal MT can be a simplified terminal for speech only or it can be a terminal for diverse services acting as a service platform and supporting the loading and execution of various functions related to the services.
Like all mobile communication systems, UMTS provides wireless data transmission services for mobile users. The system supports roaming, i.e. UMTS users can be reached and they can make calls anywhere within the UMTS coverage area. UMTS is expected to fulfil the need for a wide range of future services, such as virtual home environment (VHE). With the virtual home environment, a user has access to the same services everywhere within the coverage area of the system. Many of the services required in the future are difficult to even imagine today. The services will become more complex and they will comprise an increasing number of independent functions. It makes more sense to implement some of the services in a way that most of the functions in the service are implemented in the terminal. This way, it is possible to support roaming in particular.
A problem with the above arrangement is that one user may use completely different terminals in different situations and still want to access the same services. All functions cannot be implemented in all terminals. If only the service functions that the simplest model can execute are always implemented in a terminal, the services cannot be implemented in the most efficient way considering the whole range of terminals. If only the service functions that a mid-range terminal can execute are always implemented in a terminal, some of the services are not available in the simplest models, whereas the services could be implemented more efficiently in more complex terminals.